Multiple tunnel kiln



April 18, 1950 Filed May 29, 1948 A. B. AGNEW MULTIPLE TUNNEL KILN WQQQDQQWS "3 u n a n n u n D D U II II II I v r V V I A I I I II D D II II II II D D 3 Sheets-Sheet 1 INVENTOR. warp,

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Pussies Apr. 18. 1950 UNITED STATES PATENT OFFICE MULTIPLE TUNNEL KILN Albert B. Agnew, Philipsburg, Pa.

Application May 29, 1948, Serial No. 30,082

3 Claims.

This invention relates to new and useful improvements in the method of firing refractory products, particularly silica brick and clay brick, and it is among the objects thereof to provide a multiple kiln structure through which the product is conveyed from opposite directions in ad- Jacent kiln to efllciently utilize the heat loss in cooling the product passing from one kiln for preheating the product entering an adjacent kiln.

It is a further object of the invention to provide multiple tunnel kiln employing thin silicon carbide slabs or the equivalent thereof to form amuifie chamber from which the heat is transmitted to the product at a high degree of efficiency and the flame is not directly impinging upon the product.

Another object of the invention is the provision of a firing zone substantially centrally of the ends of the kiln in the form of a muille chamber extending the full length of the kiln to the charging end and which is open at the discharge end of the kiln, and means for drawing cooling air from the discharge end through the muiile chamber to the firing chamber and thence to the charging end for preheating the product charged into the kiln.

It is still a further object of the invention to provide a multiple kiln structure of the above designated character which shall substantially reduce the firing time for both silica and clay brick and which shall be especially adapted to the firing of various shaped clay products by the uniform application of heat to any cross sectionai area of such product.

These and other objects of the invention will become more apparent from a consideration of the accompanying drawings constituting a part hereof, in which like reference characters designate like parts, and in which- Fig. l is a top plan view schematically illustrating a complete plant for shaping and firing clay products embodying the multiple kiln structure of my invention;

Fig. 2 a vertical cross sectional view thereof taken along the line 2-2, Fig. 1;

Fig. 3 a vertical cross sectional view through the exit end of one of the multiple kiln units, taken along the line 3-3, Fig. 6;

Fig. 4 a vertical cross sectional view through the firing zone of the multiple kiln unit taken along the line 4-4, Fig. 6;

Fig. 5 a vertical cross sectional view of the charging end of one of the multiple kiln units, taken along the line 55 Fig. 6;

Fig. 6 a longitudinal cross sectional view of a multiple kiln taken along the line 6-8, Fig. 4; and

Fig. 7 a, longitudinal cross sectional view, similar to Fig. 6, with the central portion cut away to illustrate another form of blower application, as will be hereinafter explained.

With reference to Figs. 1 and 2 of the drawing, the numeral I generally designates the wall of a brick plant or the like having windows 2, columns 3 and tunnel kiln walls 4, the building being housed under a roof 5 with an elevated roof structure 6 over the multiple kiln units, as shown in Fig. 2.

The side of the plant appearing at the upper end of Fig. 1 is the railroad siding and after the raw materials have been processed they are delivered to hand molding tables I and 0, then to a dry press 9 and are conveyed on a belt conveyor III to turntables II from which they are loaded on kiln trucks for the firing process. As viewed in Fig. 1, there are four kilns designated by the numeral I2 at the upper portion thereof for drying the molded products before they are transferred to the firing kiln, which may be generally designated by the numeral IS. The space It is for the finished material, storage and shipping.

With reference to Figs. 3 to 7, the kilns are constructed of refractory and insulating materials to constitute hearth portions l5 and partition walls I6, refractory roof members l1 and insulating material II. The numeral I9 designates the kiln tunnels covered by a slab 20. The hearth of the kiln constitutes the refractory tops II of cars 22 having wheels 23 mounted on rails 24, the trucks being of suitable length and in endto-end relation whereby they are pushed from one end of the kiln to the other. The cross section of Fig. 3 shows the structure of the tunnel kiln taken along the line 3--3 of Fig. 6 which is at the charging end of the kiln, and the construction shown in Fig. 4, taken along the line 4-4 of Fig. 6, is through the firing section of the tunnel which is provided with thin silicon carbide slabs 25 to muflle the firing chambers 26 which are connected by ports 21 with air chambers 28. Burner ports 29 are in the floor of the muiile chambers through which the pipes 30 extend for connection with gas burners for firing the muflle chambers 26. In Fig. 3 a thin slab or sheet metal partition II is employed to extend the muflle chamber 26, but in the view of Fig. 5 no muflle wall is utilized at all, Fig. 5 being a Midi cross section of the discharge end of the tunnel kiln taken along the line 5-4 of Fig. 6.

Referring to Fig. 6 of the drawings, it is to be noted that there are two identically constructed tunnel kilns separated by a wall It, but the adjao ent kilns have their charging and discharge openings oppositely disposed. Thus one kiln has its charging opening, designated by the numeral 32, adjacent the discharge opening 33 of the other kiln and vice versa at the opposite end. In other words, the numeral 32 designates the chargin ends of both the kilns, and 33 the discharge 61515. At the charging end of the kilns air ducts 34 and 35 are provided which are connected to huge suction fans which function to draw air from the discharge end of the kiln, which are the openings 33, through the air chambers 28 through which it flows in the direction of the charging end of the kiln and passes through the slanting ports 2'] into'the combustion chamber 26 wherein it supports combustion of the gases delivered by the fuel pipe 30. It is then drawn through the muffle chamber 26 to the air ducts 34 and 35, from which it is delivered to the drying kiln l2 shown in the upper end of Fig. 1 of the drawing.

The purpose of the mufiie tunnel constituted by the walls 25 and 3t extending from the charging end 32 to beyond the firing zone is to draw the products of combustion from the combustion chamber 26 rearward to the charging end to preheat the clay products traveling from the charging opening 32 on the trucks 22 into the firing zone. As the trucks leave the firing zone, which is beyond the solid wall construction 35, the trucks and their refractory products are exposed to the incoming air entering through the discharge opening 33 to cool them. The incoming air is thus preheated to a very high degree before passing into the air passage 28 leading to the air ports 21. The preheated air thus supplied to the firing chambers 26 greatly increases the combustion efficiency as is well known in the art, and the products of combustion passing rearward to the charging end 32 through the muflle chamber 25 give up their heat through the thin partitions 3! to the cold trucks and refractory entering the tunnel kiln to subject them to a gradual heating before they enter the firing zone. By arranging the tunnels with the common partition wall l6 so that the charging and discharging ends of adjacent tunnels are contiguous as shown in Fig.

6, there is a heat transfer from the muflle chamher 26st the charging end of the tunnel through the partition wall It to the discharge end of the adjacent tunnel, thereby supplying additional heat for preheating the air drawn into the ad- Jacent tunnel from the discharge end thereof.

The above described heating of the kiln with the location of the suction ducts 34 and 35 in the mume chambers 26 is especially for use in burning silica brick or clay products of similar composition. This is so because there is no ignition loss in silica brick if it is dried to 210 F. In ordinary clay brick, however, an increased volume of air is required to contact the clay to remove increased moisture that is present. This is accomplished as shown in Fig. 7 by putting the suction air ducts designated by the numeral 38 in the tunnel kiln instead of the muiile chambers at the charging end of the kiln. By means of the above described multiple tunnel kiln with adiacent tunnels charged from opposite ends to recover heat loss by radiation for preheating ad Jjacent-sections of tunnels, the average time for burning silica brick is reduced from nine to twelve days to to hours, and the average time for burning clay brick is reduced from seven days to cool and four or five days to empty and clean the kiln, to from 46 to 48 hours. These time averages vary more or less with the particular shapes being burnt.

By means of the above described multiple kiln for burning clay products, the brick or other products are burned continuously and more uniformly because there aresmaller masses of the product passing through'the temperature controlled tunnel kiln. Also, improved multiple kiln are more efficient in burning odd shapes of clay products of varying cross sectional areas because they are more uniformly exposed to the heating and cooling mediums in their passage through the tunnels. As shown in Fig. 4 of the drawings, the hearth trucks have depending sealer plates I9 that are disposed in troughs 40 which may be filledwith sand to seal the kiln tunnels, if desired. Also, there is no accumulation of materials that require frequent cleaning as in conventional .and an open hearth bottom provided with rails for supporting wheeled trucks having a refractory hearth forming a continuous movable hearth throughout the length of the tunnel for supporting fire brick or the like, said outer walls having parallel walls spaced therefrom constituting the firing pone of the kiln, said walls having ports for admitting air and forming a chamber open at one end and sealed at the other so that air drawn into said chamber between the outer and inner walls through the open end will pass through the openings or ports of the inner wall, a muille wall extending parallel with the ported wall of the firing zone the full length and rearward to the charging end of the tunnel to constitute a mufllechamber through the firing zone and the full length from the firing zone to the charging end, and suction ducts in said muiiie chambers at the charging end of the tunnel to draw air from the discharge end of the tunnel through the ports into the muilie chamber to support combustion in the firing zone and to draw the products of combustion along the muffle chamber to the charging end thereof.

2, In a multiple kiln for burning clay products, a tunnel of refractory material having a partition wall dividing the same into two elongated chambers constituting adjacent tunnel kiln, each chamber having rails for supporting trucks constituting movable hearths adapted for movement in opposite directions in adjacent tunnels, said tunnels having inner walls parallel mm the outer and partition walls for a substantial distance spaced from the ends of the tunnels constituting firing zones, said spaced walls having ported passages and forming chambers open towards the discharge end of the tunnels and closed toward the charging ends thereof, muiiie walls spaced from and extending the length of the inner walls and beyond the inner walls to the charging end of the tunnels, said muiile walls being sealed with the inner walls toward the discharge end 01' the tunnel to form closed muflle chambers through the length of the firing zone and all the way back to the charging end of the tunnels except for the ported passages in the parallel walls, said muflle chambers having exhaust ducts at the charging end of the tunnel whereby air is drawn through the discharge end over the burnt clay products passing out of the tunnel into the chambers between the parallel walls, the outer walls and partition walls of the tunnels and through the ports into the muiile chambers to support combustion, and thence with the products of combustion are drawn rearward through the mufile chambers toward the charging end of the tunnel.

3. A tunnel kiln comprising a plurality of parallel outer walls of a refractory material, a roof at the top and an open hearth bottom provided with rails for supporting wheeled trucks having a. refractory hearth forming a continuous movable hearth throughout the length of the tunnel for supporting fire brick or the like, said outer walls having parallel walls spaced therefrom extending -a substantial distance through the length of the tunnel to constitute the fire zone of the 6 kiln, said walls having ports for admitting air and forming a chamber open at one end and sealed at the other so that air drawn into said chambers between the outer and inner walls through the open end will pass through the openings or ports of the inner wall, burners disposed in longitudinal spaced relation in the tunnel inside of the inner parallel walls, and suction means in said tunnel at the sealed end of said parallel walls to draw air through the ports from the open end of the pair of walls into the tunnel chamber.

ALBERT B. AGNEW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Hanley, Jr Jan. 18, 1927 

